Debilitating movement disorders have been treated by non-reversible surgical ablation of affected brain circuits by thalamotomy or pallidotomy, for example. Deep brain stimulation (DBS) therapy is an attractive alternative to such permanent surgeries, providing the distinct advantages of reversibility and adjustability of treatment over time. DBS is a treatment method that aims to change the rates and patterns of activity of brain cells by implanting a brain stimulator (i.e., an electrode, also known as a lead) into a target region in the brain known to be associated with movement, such as the thalamus, subthalamic nucleus (STN), globus pallidus, internal capsule, and nucleus accumbens.
Electrical stimulation by DBS of a particular target region of the brain, in some cases bilaterally (i.e., using an electrode on each side of the brain to stimulate paired target regions located on each side of the brain), has been successfully used to treat symptoms of several movement disorders. For example, it has been reported in several studies that targeting of the STN is effective to alleviate symptoms of Parkinson's disease. To date, all DBS applied to humans in FDA-approved clinical trials are conducted with regular isochronous stimulation; that is, the pulses of electrical stimulation are evenly distributed in time. Parkinson's disease and essential tremor, for example, are typically treated with high frequency isochronous stimulation at 130 Hz or greater.